Antenna array and method for generating a high intensity electromatic pulse

ABSTRACT

An apparatus and a method for providing a uniform, high intensity, transverse electromagnetic pulse for illuminating a large area, such as a zone 40 meters by 40 meters. An array of horn radiators constructed in modules and fed from parallel transmission lines. A pulse generator including a plurality of high voltage capacitors, a DC supply for charging the capacitors, and a switch for discharging the capacitors into corresponding transmission lines to provide voltage pulses at each horn, with the resulting electromagnetic pulses producing a composite electromagnetic pulse of total voltage many times the voltage of the supply.

United States Patent 72] Inventor Jacob J. Gustincic Los Angeles, Calif.

[211 App]. No. 17,148 i [22] Filed Mar. 6, 1970 [45] Patented Nov. 9, 1971 [7 3] Assignee Radyne, Inc.

Chatsvrorth, Calif.

[54] ANTENNA ARRAY AND METHOD FOR GENERATING A HIGH INTENSITY [56] References Cited Primary Examiner-Terrell W. Fears Assistant Examiner-Stuart I-Iecker Attorney-Harris, Kiech, Russell & Kern ABSTRACT: An apparatus and a method for providing a uniform, high intensity, transverse electromagnetic pulse for illuminating a large area, such as a zone 40 meters by 40 meters. An array of horn radiators constructed in modules and fed from parallel transmission lines. A pulse generator including a plurality of high voltage capacitors, a DC supply for charging the capacitors, and a switch for discharging the capacitors into corresponding transmission lines to provide voltage pulses at each horn, with the resulting electromagnetip pulses producing a composite electromagnetic pulse of total voltage many times the voltage of the supply.

PATENTEUNuv span.

PQ one on INVENTOR. J/qcoa J. Guam/cm. BY HIS ATTORNEYs,

HARRIS/066M Russeu & KERN.

tromagnetic pulse with a voltage gradient of 50,000 volts per meter across a 40-meter aperture. The area illuminated may be 40 meters by 40 meters.

The conventional approach to this requirement has been to feed a parallel plate structure with a pulse generator having the required voltage output, namely gradient times aperture of 50,000 volts X 40 meters, calling for a pulse generator with a 2,000,000-volt output pulse. The problems encountered in producing and handling a 2,000,000-volt pulse are readily apparent.

It is an object of the present invention to provide new and improved methods and apparatus for producing electromagnetic pulses of relatively high voltage gradient utilizing a relatively low voltage source. a further object is to provide an array of horn radiators disposed over the area to be illuminated, with the radiators fed in parallel from the low voltage supply and with the resultant electromagnetic pulses from the radiators forming a composite output pulse having thedesired high voltage gradient. A particular object of the invention is to provide such a structure which may be modular in nature and which is readily erected, taken down, and transported.

It is aparticular object to provide such process and apparatus wherein the angle of the arrival or incidence of the electromagnetic wave and the polarization. of the radiation may be controlled and varied so as to provide a normally incident wave or an obliquely incident wave, as desired.

In the preferred embodiment illustrated herein, a transverse electromagnetic plane wave is guided by a parallel plate transmission line to the area to be illuminated by the electromagnetic pulse. The transverse electromagnetic wave pulse is produced or launched by a uniformly spaced, uniformly phased, equal amplitude planar array at the input of the parallel plate line. Each element of the array is a square aperture, transverse electromagnetic horn formed by a pair of plates or screens linearly tapered in the planes of the electric and magnetic fields. The side ofeach horn aperture is one-half wavelength long, based upon the highest frequency component of the pulse to be launched. The horns are fed from a plurality of parallel coaxial transmission lines which are energized by a pulse generator comprising a DC voltage supply, a plurality of high voltage capacitors and a switch for connecting the capacitors to the transmission lines.

The system of the present invention makes use of the apparent isolation provided by a length of transmission line having an electrical length greater than the width or duration of the voltage pulse, to spatially redistribute the energy provided by the voltage source over a large area. A uniform electric field is produced over a large surface without requiring the use of very high voltage generators as required in the aforementioned parallel plate system. The voltage required in the system of the present invention is a fraction of that used with prior art systems, with the ratio being determined by the number of transmission paths between the voltage source and the radiator array. The system of the present invention may be considered a parallel-to-series system, as opposed to the prior art series-to-series systems.

Other objects, advantages, features and results will more fully appear in the course of the following description. The drawing merely shows and the description merely describes a preferred embodiment of the present invention which is given by way of illustration or example.

In the drawing:

FIG. 1 is an isometric vview of a modular array illustrating a preferred embodiment of the present invention;

FIG. 2 is a diagrammatic illustration of a large array incorporating several of the modules of FIG. 1;

FIG; 3 is an electrical diagram illustrating the pulse generator and the transmission lines connecting the pulse generator to the radiators; and

FIG. 4 is an enlarged sectional view along the line 4--4 of FIG. 1.

FIG. 1 illustrates a portion of an array of radiators, comprising two dual modules 10, 11. Each dual module has two pairs of plates,.l2, 13, 14, 15, with a pair (e.g. 12 and 13) forming two dihedral horn radiators. Typically a plate 12 includes two metal screens 20, 21 and screen support rods 22, 23, 24, 25, 26, and 27. Screening is normally used in lieu of sheet material because of lower weight and cost and lower wind resistance. The screen 20 of the plate 12 and the corresponding screen 30 of the plate 13 coact to form one horn.

The horns may be supported by various structural arrangements and a preferred support structure is illustrated in FIG. 1. The support structure assembly is a prefabricated modular system utilizing electrically nonconducting beams, typically of fiberglass, thus providing easy field assembly and disassembly and transportation, and being readily adaptable to a variety of installation configurations. The support structure is designed to allow assembly in the horizontal plane over the surface of the earth or over the roofs of buildings and the like to provide vertical incidence angles. The structure may also be assembled vertically against the side of a building to provide horizontal incidence angles.

The support structure includes a post 31 at each comer of a module, with asupport pad 32 at the lower end of the post. The posts 31 are interconnected by horizontal trusses 33 which may be affixed to the posts at connection plates 34, typically with clevis and pin connections.

In the preferred embodiment illustrated, the output apertures of the horns are square so that a dual module is also square and the same truss 33 can be used for all sides of the structure. Theposts and trusses are made of a nonconducting material, typically fiberglass.

One embodiment of the system utilizes 576 horns in an array of 24x24, requiring 144 dual modules. Each horn output aperture is 5% feet square making a module 1 l feet X l 1 feet, with the array 132 feet X 132 feet, illuminating an area approximately 40 meters square.

The plate 12 is affixed to a truss by laterally projecting rods 38, 39 carried on the plate and positioned in clamps 40, 41 carried on the truss.

The array of horn radiators functions as a launcher. for the electromagnetic pulse. A parallel plate transmission line may be provided to guide the pulse as a transverse electromagnetic plane wave, from the array to the area to be illuminated. Conducting sheets may be affixed at opposite edges of the array to serve as the parallel plate transmission line, and a typical conducting sheet 42 shown in FIG. 1. This sheet 42 may be a screen of conducting material with peripheral support rods 43, with the sheet supported on the trusses and electrically connected to the adjacent plates. In a typical installation, the sheet 42 may be in the order of 30 feet long.

The rod 27 of the plate 12 and the adjacent rod 44 of the plate 13 are of electrical conducting material and form an open twin conductor line for feeding in parallel the two horns formed by the plates 12, 13 Electrical connection is made to the rods 27 and 44 by snap-on connectors 45, 46 carried in a connector block 47 (FIG. 4).

An end view of an array incorporating the dual module 10 of FIG. I is shown diagrammatically in FIG. 2. In the specific example given, the outlet aperture of one horn is 5% feet and the output aperture of the array is I32 feet. With an electromagnetic pulse from a horn of 80,000 volts and with the horns uniformly phased ,and having outputs of equal amplitude, the voltage at the aperture of the array is 1,920,000 volts.

The equal amplitude and uniform phasing is obtained by driving the horns of the array in parallel from a suitable pulse generator, such as that illustrated in Fig. 3, via a plurality of parallel transmission lines. A DC power supply 52 is connected to one plate of each high voltage capacitor 51 of a parallel ensemble with the other plate of each capacitor 51 connected to circuit ground, along with the outer conductor or shield 49 of a transmission line 53. A single-pole singlethrow switch 50 is used to connect these capacitors to the inner conductors of the transmission lines 53 which run to horns of the array.

ln'the preferred embodiment illustrated, the line 53 is a coaxial conductor and runs to a tee unit 54, with the center conductor of the line 53 connected to the center conductors of lines 55, 58 and with the outer conductor of the line 53 connected to the center conductor of lines 57, 56. The lines 5558 preferably are coaxial lines, with their outer conductors connected together. The center conductor of the line 55 is connected to the clamp 46 and the center conductor of line 57 is connected to the clamp 45 completing the path to the horns formed by the plates R2, 13. The lines 56 and 58 are similarly connected to another pair of plates, which may be the plates M, 15 of the dual module 110 or another pair of plates in another module, such as the dual module 11 as illustrated in FIG. 1. IN an alternate arrangement, a separate transmission line may be used for each born or for each pair of horns.

In the embodiment illustrated with 576 horns, 144 transmission lines 53, .tee units 54, and high voltage capacitors 51 will be required. The switch S simultaneously discharges the 144 capacitors 51 into the respective transmission lines 53. The width of the output pulse is determined by the amount of energy stored in the capacitors. The power supply 52 is a high voltage DC supply, and typically may comprise one or more conventional 100 kv. units connected in series providing 18 milliamperes of output current which will charge all of the capacitors 511 to full voltage in a few seconds. The specific voltage level may be adjusted by conventional controls at the input to the power supply.

After the high voltage capacitors 51 are charged from the power supply 52, each capacitor is discharged into the corresponding transmission line 53 by the switch 50. The switch 50 is preferably a high speed switching unit and typically may be a solid-state dielectric unit providing a high rise time are with high peak current handling capability. A typical peak switch current may be 250 kiloamperes, providing a voltage pulse in the order of 80,000 volts peak and 350 nanoseconds duration.

The electrical length of the transmission line from the switch to a horn preferably is greater than the duration of the voltage pulse, providing time isolation which insures that reflections from the horns do not interfere with the pulse being delivered by the pulse generator. Typically the transmission line is 250 feet in length or an electrical length of 400 nanoseconds. When the length of line from the switch to each horn is the same, the composite electromagnetic pulse from the array will be normally incident. Different angles of incidence may be achieved by progressively increasing the length of the transmission line to each horn across the array, introducing time delays in the pulse arrival at each horn, with a resultant obliquely incident output from the array. All of the transmission lines may be conventional 50-ohm coaxial line which is inexpensive, readily available and easily inspected electrically.

The system of the present invention provides an electromagnetic pulse with a very high voltage gradient over a very large area without requiring a correspondingly high voltage from the power source. This is accomplished by utilizing a DC source to charge a plurality of capacitors in parallel and then simultaneously discharging all of the capacitors into a plurality of transmission lines (each capacitor into its own transmission line) to an array of radiators or launchers which produce electromagnetic fields which combine in series to provide the desired high intensity output. The power source for the present system delivers the same amount of energy as does the power source of the conventional system which operates at the much higher input voltage. However, the power source operates at a much lower voltage, which greatly simplifies the problems of construction and maintenance and substantially reduces the initial cost as well as maintenance and operating costs. Although an exemplary embodiment of the invention has been disclosed and discussed, it will be understood that other applications of the invention are possible and that the embodiment disclosed may be subjected to various changes, modifications and substitutions without necessarily departing from the spirit of the invention.

lclaim:

1. In apparatus for providing a uniform, high intensity, transverse electromagnetic pulse for illuminating a large area, the combination of;

a plurality of dihedral horn radiators;

means for mounting said horns in a uniform array of rows and columns;

each of said horns including a pair of opposed conducting sheets, with the convergent ends of said sheets spaced apart to form an input aperture; and

a plurality of transmission lines connected in parallel to said horns at the input apertures thereof.

2. Apparatus as defined in claim 1 including a pulse generator coupled to each of said transmission lines for delivering a voltage pulse to each of said horns in parallel.

3. Apparatus as defined in claim 1 including a transmission line for the output pulse of the array comprising parallel conducting sheets affixed to the outer edges of the output apertures of the outer horns of said array and projecting away from said horns.

4. Apparatus as defined in claim 1 in which two of said horns are formed in a module comprising a pair of plates,

each of said plates having two of said conducting sheets joined together at the output ends thereof and connected together at the input ends thereof by an elongate conductor,

with said elongate conductors forming an open twin conductor transmission line for the input to each horn of the module.

5. Apparatus as defined in claim 2 in which the electrical length of each of said transmission lines is greater than the duration of the voltage pulse from said generator.

6. Apparatus as defined in claim 5 in which each of said transmission lines is the same length providing a normally incident electromagnetic pulse.

7. Apparatus as defined in claim 5 in which the length of said transmission lines are progressively increased across the array providing an oblique incident electromagnetic pulse.

8. Apparatus as defined in claim 4 in which a transmission line includes first, second, third, fourth and fifth coaxial lines, with the first line center conductor connected to the center conductors of the second and third lines at a tee, and with the first line outer conductor connected to the center conductors of the fourth and fifth lines at said tee, and with said second and fourth lines running in parallel to one of said open twin conductor lines, and with said third and fifth lines running in parallel to another of said open twin conductor lines.

9. Apparatus as defined in claim 2 in which said pulse generator includes:

a plurality of high voltage capacitors;

a DC power supply for providing a charging current;

first connecting means for connecting each of said capacitors to said power supply in parallel for charging the capacitors; and

second connecting means for connecting each of said capacitors simultaneously to a transmission line for delivering a voltage pulse to the transmission line, said second connecting means including a switch which is open during capacitor charging from said power supply and closed for capacitor discharging into a transmission line.

10. A method of generating a unifonn, high intensity, transverse electromagnetic pulse to a large area, including steps of:

generating a plurality of charges on a plurality of capacitors by connecting the capacitors in parallel to a relatively low voltage DC power supply; and

lines substantially equal so that the composite electromagnetic pulse is normally incident.

12. A method as defined in claim 10 including progressively increasing the transit time of the charges along the transmission lines from one edge of the array to the opposing edge so that the composite electromagnetic pulse is obliquely incident.

i i i 4 UNITED STATES PATENT OFFICE CERTIFICATE OF CGRRECTION Patent Nmj .619 639 Dated November 9, 197].

Inventor(s) Jacob J. Gustincic It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

Title page Column 1, and column 1, line 3 of patent,

title of invention should be "ANTENNA ARRAY AND METHOD FOR GENERATING A HIGH INTENSITY ELECTROMAGNETIC PULSE Column 1, line 15, "of" should be -or--;

line 74, "large" should be ---larger--.

Column 6, line 4, "time" should be --times--.

Signed and sealed this 25th day of April 1972.

(SEAL) Attest 2 EDWARD I LFLE'I'CHER, JR. OBERT GOTTSCHALK Attes'ting Officer Commissioner of Patents EM PO-1050 (10-69) USCOMM-DC 60376-Po9 Q u.s, covsmmzm HUNTING OFFICE: I969 mun-3:4 

1. In apparatus for providing a uniform, high intensity, transverse electromagnetic pulse for illuminating a large area, the combination of; a plurality of dihedral horn radiators; means for mounting said horns in a uniform array of rows and columns; each of said horns including a pair of opposed conducting sheets, with the convergent ends of said sheets spaced apart to form an input aperture; and a plurality of transmission lines connected in parallel to said horns at the input apertures thereof.
 2. Apparatus as defined in claim 1 including a pulse generator coupled to each of said transmission lines for delivering a voltage pulse to each of said horns in parallel.
 3. Apparatus as defined in claim 1 including a transmission line for the output pulse of the array comprising parallel conducting sheets affixed to the outer edges of the output apertures of the outer horns of said array and projecting away from said horns.
 4. Apparatus as defined in claim 1 in which two of said horns are formed in a module comprising a pair of plates, each of said plates having two of said conducting sheets joined together at the output ends thereof and connected together at the input ends thereof by an elongate conductor, with said elongate conductors forming an open twin conductor transmission line for the input to each horn of the module.
 5. Apparatus as defined in claim 2 in which the electrical length of each of said transmission lines iS greater than the duration of the voltage pulse from said generator.
 6. Apparatus as defined in claim 5 in which each of said transmission lines is the same length providing a normally incident electromagnetic pulse.
 7. Apparatus as defined in claim 5 in which the length of said transmission lines are progressively increased across the array providing an oblique incident electromagnetic pulse.
 8. Apparatus as defined in claim 4 in which a transmission line includes first, second, third, fourth and fifth coaxial lines, with the first line center conductor connected to the center conductors of the second and third lines at a tee, and with the first line outer conductor connected to the center conductors of the fourth and fifth lines at said tee, and with said second and fourth lines running in parallel to one of said open twin conductor lines, and with said third and fifth lines running in parallel to another of said open twin conductor lines.
 9. Apparatus as defined in claim 2 in which said pulse generator includes: a plurality of high voltage capacitors; a DC power supply for providing a charging current; first connecting means for connecting each of said capacitors to said power supply in parallel for charging the capacitors; and second connecting means for connecting each of said capacitors simultaneously to a transmission line for delivering a voltage pulse to the transmission line, said second connecting means including a switch which is open during capacitor charging from said power supply and closed for capacitor discharging into a transmission line.
 10. A method of generating a uniform, high intensity, transverse electromagnetic pulse to a large area, including steps of: generating a plurality of charges on a plurality of capacitors by connecting the capacitors in parallel to a relatively low voltage DC power supply; and at one time transmitting each charge to a corresponding one of a plurality of radiators providing a voltage pulse to the radiator, with the plurality of radiators disposed in an array so that the electromagnetic pulses from the radiators produced by the voltage pulses, are in series resulting in a composite electromagnetic pulse of relatively high voltage.
 11. A method as defined in claim 10 including maintaining the transmission times of the charges along the transmission lines substantially equal so that the composite electromagnetic pulse is normally incident.
 12. A method as defined in claim 10 including progressively increasing the transit time of the charges along the transmission lines from one edge of the array to the opposing edge so that the composite electromagnetic pulse is obliquely incident. 